import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int l = in.nextInt();
        int r = in.nextInt();
        int count = 0;
        for(int i = l; i <= r; i++) {
            int val = i;
            while(val != 0) {
                int cur = val % 10;
                if(cur == 2) count++;
                val /= 10;
            }
        }
        System.out.print(count);
    }
}